How should the success of river and floodplain restoration be assessed? What should we be restoring? We contend that the benchmark for restoration should be the river in its “natural,” that is, quasi‐equilibrium condition prior to deliberate modification. The pre‐modification condition of the river represents a quasi‐equilibrium state in which the river accommodates and adjusts to catchment water and sediment fluxes, whether in a pristine or modified catchment. The resulting assemblage of river landforms (e.g., bars, channels, backwaters) is in balance with the prevailing flood and sediment regime. Furthermore, equilibrium channel forms can adjust to changes in, for example, flood magnitude and frequency via for example, channel expansion or contraction. A restored river system is one that once was anthropogenically restricted, but now has regained capacity to adjust its form. River restoration needs understanding of the history and trajectory of pre‐modification channels, so that the “right” river type can be restored. To assess the scope and success of restoration, we propose using a natural character index (NCI). The NCI is the ratio between a parameter which describes the form and function of a river now (observed) and the same parameter measured at a point or points in time past (expected). Exemplar parameters include sinuosity, floodplain width, active channel width, bar area (at a given flow) and riparian vegetation. Measurement of these parameters utilizes a combination of aerial photos, archive maps and LiDAR‐derived terrain models, the availability of which necessarily limits and determines what parameters can be used in NCI assessment. LiDAR is a useful tool providing an opportunity to comprehend pre‐modification river and floodplain character. We illustrate the NCI concept and its potential for use in assessing restoration effects using examples from New Zealand, Spain and Croatia. The result is an index of use as a “first cut” preliminary assessment for river practitioners.

中文翻译：

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评估河流和洪泛区恢复的程度和成功的指数：识别动态响应轨迹并应用基于过程的方法来管理河流恢复

应该如何评估河流和洪泛区恢复的成功？我们应该恢复什么？我们认为，恢复的基准应该是河流在其“自然”状态下，即在有意修改之前的准平衡条件。河流的变质前状态代表着一种准平衡状态，在该状态下，无论原始流域还是变质流域，河流都能适应流域的水和沉积物通量并对其进行调整。河流地貌的集合（例如，条形，河道，死水）与普遍的洪水和沉积物状况保持平衡。此外，平衡通道形式可以通过例如通道膨胀或收缩来适应例如洪水幅度和频率的变化。恢复的河流系统曾经是人为限制的，但现在已经恢复了调整形式的功能。河流恢复需要了解预先改造渠道的历史和轨迹，以便可以恢复“正确”的河流类型。为了评估修复的范围和成功与否，我们建议使用自然特征索引（NCI）。NCI是描述河流的形式和功能的参数（观测到的）与在过去一个或多个时间点测得的相同参数（预期的）之间的比率。示例性参数包括弯曲度，洪泛区宽度，活动河道宽度，钢筋面积（在给定流量下）和河岸植被。这些参数的测量结合了航拍照片，档案图和LiDAR衍生的地形模型，其可用性必然会限制并确定可以在NCI评估中使用的参数。LiDAR是有用的工具，可提供理解河床和洪泛区特征的预修改的机会。我们以新西兰，西班牙和克罗地亚为例，说明了NCI概念及其在评估修复效果中的潜力。结果是用作对河道从业者的“首次切割”初步评估的指标。